# vtkXMLPUnstructuredGridWriter.h is missing
**URL:** https://discourse.vtk.org/t/vtkxmlpunstructuredgridwriter-h-is-missing/7922
**Category:** Support
**Created:** [February 25, 2022, 9:39am UTC](https://discourse.vtk.org/t/vtkxmlpunstructuredgridwriter-h-is-missing/7922 "2022-02-25T09:39:20Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Marshdweller](https://discourse.vtk.org/u/Marshdweller)
#### Post date: [February 25, 2022, 9:39am UTC](https://discourse.vtk.org/t/vtkxmlpunstructuredgridwriter-h-is-missing/7922/1 "2022-02-25T09:39:20Z")
I am trying to link an existing software to VTK9.1, and keep getting a compile-time error “vtkXMLPUnstructuredGridWriter.h not found”. It is indeed missing from the …/include directory, although vtkXMLPUnstructuredGridReader.h is there.
I built VTK with USE\_MPI=ON and VTK\_GROUP\_ENABLE\_MPI=YES, but it does not help.
What should I check? Any advice is appreciated.
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### Author:  [@mwestphal](https://discourse.vtk.org/u/mwestphal)
#### Post date: [February 25, 2022, 9:42am UTC](https://discourse.vtk.org/t/vtkxmlpunstructuredgridwriter-h-is-missing/7922/2 "2022-02-25T09:42:54Z")
@ben.boeckel
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### Author:  [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [February 25, 2022, 12:59pm UTC](https://discourse.vtk.org/t/vtkxmlpunstructuredgridwriter-h-is-missing/7922/3 "2022-02-25T12:59:10Z")
The MPI group doesn’t interact with the `VTK::IOParallelXML` module, so that makes sense. Please make sure that the module is available. Note that the reader is in `VTK::IOXML`, so the presence of the reader does not imply the availability of the writer.
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### Author:  [@Marshdweller](https://discourse.vtk.org/u/Marshdweller)
#### Post date: [February 25, 2022, 1:28pm UTC](https://discourse.vtk.org/t/vtkxmlpunstructuredgridwriter-h-is-missing/7922/4 "2022-02-25T13:28:45Z")
It seems to be the solution. I toggle the advanced mode [t] in ccmake and enabled IOParallelXML manually. Thank you!